The E Ride Nights were only at the MK, and carried a $10 fee, but they were less crowded than the new Extra Magic Hours that replaced them.
The old E-Ride nights (not to be confused with the new EMH nights) were wonderful. For around $10, on select nights, you had an extended stay in the Magic Kingdom for 3 hours. Unlike EMH nights, the E-Ride nights were not really publicised, and hardly anyone knew about them. This meant that there really were very few people in the park. They have now been discontinued and replaced by the current Extra Magic Hour nights, which are free to resort guests.
It's like having FastPasses to the most popular MK attractions except for Space Mountain, which tends to have a slightly longer wait time (15-20 minutes). Everything else? Less than 10 minutes. The atmosphere is festive, and while the average age is higher than during the day, there are still plenty of younger kids there, as well. My only complaint: more of the food carts should remain open.
I only went once because I usually go in the first two weeks of December and the event is cancelled during December because of Mickey's Very Merry Christmas Party and the Christmas season is general but the event is a big must if you have too much to do to get on the thrill ride like Big Thunder Mountain Railroad, Splash Mountain and Space Mountain during the early morning.